Isolation Valve Research Articles

Management of water distribution systems in PDA conditions using isolation valves: case studies of real networks

Abstract The current paper reports on a case study investigating water distribution system management in emergency conditions when it is necessary to seal off a zone with isolation valves to allow repair. In these conditions, the pressure-driven analysis (PDA) is considered to be the most efficient approach for the analysis of a water distribution network (WDN), as it takes into account whether the head in a node is adequate to ensure service. The topics of this paper are innovative because, until now, previous approaches were based on the analysis of the network behaviour in normal conditions. In emergency conditions, it is possible to measure the reliable functioning of the system by defining an objective function (OF) that helps to choose the optimal number of additional valves in order to obtain adequate system control. The OF takes into account the new network topology by excluding the zone where the broken pipe is located. The results show that the solution did not improve significantly when the number of valves reached a threshold. The procedure applied to other real case studies seems to confirm the efficiency of the methodology even if further examination of other cases in different conditions is necessary.

Considerations on transients in a water supply distribution network

Lipnița is a village situated in a hilly region, in Constanta County. The water supply system has its own groundwater water source, placed in the middle of the village at a low elevation. Water is conveyed, by a long transmission duct to a storage tank from which it flows by gravity to the consumers. The distribution network has two long mains that intersect in a manifold with isolation valves, situated in the middle of the village. This topology of the system shows high static head for the transmission duct and high elevation differences between the end consumers and those in the centre of the village.The paper presents an analysis, by numerical simulation, on the transients that occur in two different segments of the system.The simulation was performed either for the original old steel made network, aiming at identifying the vulnerable cross sections and extreme pressure values. The results showed that maximal pressure values are not dangerous, but cavitation occurs along the pipeline. The same simulation was carried out for the new PEHD pipelines. The change of material and the increase in diameter of the new pipes showed better results regarding pressure variation during transients. Cavitation is avoided.

Algorithmic support of automatic yield control system of a gas well cluster

Gas wells operation is associated with the problem of regulating their yield. Debit value must provide for meeting various criteria with some of them being mutually exclusive. Initial debit value is set under a deposit development project and then is adjusted periodically at best based on the results of quarterly hydrodynamic well exploration. However, in order to enhance operation yield of a gas well cluster debit regulation must be carried out in real time. This problem hasn’t been solved yet. The article offers a yield control algorithm for a gas well cluster consisting of three separate units: yield enhancement, yield decreasing and yield distribution among wells. Transfer from one unit to another is carried out based on the results of measuring current gas consumption rate in wells and the pressure on isolation valve building’s plumes. The gap between the allowed values of well consumption (maximum and minimum) is identified on the basis of the research of a well’s operation. Algorithm approbation was carried out in a program package for simulation, design and analysis of the operation of above-ground infrastructure and PipeSim pipeline system. The results confirmed the feasibility of the proposed algorithm and the possibility of managing operation regime of every well independently.

High-Power Testing of Guided-Wave Components for the ITER ECH Upper Launcher at the FALCON Test Facility

Each of the four ITER electron cyclotron heating (ECH) upper launchers (ULs) features eight transmission lines (TLs) made of guided-wave components used to inject 170-GHz microwave power into the plasma at a level of up to 1.31 MW per line, at the TL diamond window unit (DWU). The guided-wave components include a DWU, an isolation valve (IV), waveguides (WGs), and miter bends (MBs). These form part of the first confinement system (FCS) of the ITER UL. They must withstand the nominal mechanical structural stresses, the electromagnetic forces, and the dynamic loads (VDE, MD, and Seismic), while being compatible with the most stringent ITER vacuum and safety classification. Here, we report new results on plans for high-power testing of guided-wave components that the Swiss Plasma Center (SPC) of the Swiss Federal Institute of Technology Lausanne (EPFL) has developed for the FCS. FALCON is home to testing equipment provided by Fusion for Energy (F4E) and ITER, including an ITER-grade 170-GHz GYCOM gyrotron and a matching optics unit (MOU), an evacuated TL including a power monitor MB (PMMB), a downtaper (DT) to the 50-mm ITER TL diameter, and a matched RF load (RFL). The facility is operated by the SPC.

Water Distribution Network Reliability Assessment and Isolation Valve System

Mechanical reliability analysis of water distribution networks (WDNs) refers to the assessment to provide correct service to customers under abnormal functioning conditions due to system component failures. Mechanical reliability depends on the isolation valve system (IVS) effectiveness in isolating a network segment and on the failure probability. The main aim of this work was the formal development of reliability indicators considering pressure-driven analysis (PDA) for customer demand and topological changes. Three factors influencing reliability were identified: (1) the hydraulic behavior of the still-connected network; (2) the topological performance of the IVS; and (3) the topological performance of the IVS with respect to unintended isolation. The reliability performance assessment of the network over time depends on the hydraulic capacity of the WDN under abnormal functioning conditions and on two IVS performance topological indicators of the risk of disconnection and unintended isolations. The hydraulic capacity was computed using PDA, whereas the topological risks were computed considering the unsupplied demand in the isolated segment and the normalized failure probability, i.e., the probability of a segment disconnection for an assumed failure occurrence in the network. The development of a modularity index for an IVS was achieved in a consistent framework and the integrated design of an IVS and district metering areas was introduced. The framework allows the analysis of the isolation valve failure. A real Apulian WDN was used to discuss and demonstrate the theoretical findings.

Dual topology for partitioning of water distribution networks considering actual valve locations

ABSTRACTThis paper proposes a general framework to adjust water distribution network (WDN) partitioning algorithms to account for the real positions of isolation valves. It is based on changing the reference WDN topology, on which partitioning algorithms typically operate. Specifically, the WDN topological description based on nodes and pipes must be replaced with a dual topology based on WDN segments and isolation valves. A generic partitioning algorithm can then be applied to the dual topology. As a result, DMAs are obtained by merging adjacent segments while inter-DMA boundary pipes are forced to be selected among the valve-fitted pipes that separate segments. This framework enables obtaining feasible WDN partitioning solutions, which do not need additional isolation valves to be installed. The applications of the novel framework to three WDN partitioning algorithms prove its effective applicability in one explicatory WDN and two WDNs of the real world.

Back pressure optimization of direct air-cooled condenser considering anti-freezing and low-load operation

Direct air-cooled condensers are widely applied in northwest China because of water-saving. In order to improve the economical operation of the direct air-cooled condenser, based on the mechanism model, this paper calculates the optimal back pressure considering anti-freezing and low-load operation with considering the switching state of the exhaust steam isolation valves, and ensuring the minimum exhaust steam. The influences of ambient temperature and load ratio on optimal back pressure and energy saving are studied, which provide guidance for cold-end optimization and economic operation of direct air cooled condensers.

Dynamic risk assessment approach of riser recoil control failure during production test of marine natural gas hydrate

AbstractThe marine natural gas hydrate is considered to have huge resource potential in the South China Sea, and a sixty‐day production test has been successfully conducted in 2017. As the crucial and most vulnerable connection of floating platform and subsea wellhead, the risers are of paramount importance in safe production test of the hydrate. Due to harsh environment and the possible drive off and drift off events induced by failure of dynamic positioning system of the platform, the unplanned emergency disconnect of risers is an integral preventive measure to avoid accidents and secure the well. Once the disconnect occurs, the huge potential energy stored in the riser column will release and consequently cause violent axial recoil, which will cause serious consequences if the recoil control fails. This paper presented a quantitative risk assessment approach on the basis of dynamic Bayesian networks to dynamically predict the risk of riser recoil control failure during production test of hydrate. By using the proposed method, the dynamic failure risk of the riser recoil control was figured out, and the most contributory factors were identified. The practical application of the proposed methodology was demonstrated through a case study. Results indicated that the probability of riser recoil control failure can be significantly decreased within one year through equipment repair, and the failure and repair rates of shutoff valves and main air isolation valves are the most contributory factors. Some corresponding safety control measures were proposed to further mitigate the risk of riser recoil control failure during the production test of hydrate.

Establishing compatibility of technical elements for electric isolation valve systems

This research addresses the issue of technical compatibility of elements. It demonstrates that violation of technical compatibility principles when engineering products are designed reduces the quality and increases energy intensity of systems. It is established that for electric isolation valves, the main performance indicator of element compatibility is as follows: the ratio of energy flows expended on deformation of isolation and force-measuring springs. To meet the requirements for compatibility of technical elements in electric isolation valve systems, it is recommended to expand the number of indicators in project documentation. Key indicators should include variations of output characteristics by different combinations of such parameters, as the electric drive rotational speed, control system lag time, stiffness of the force-measuring spring and isolation valves.

Imperfect Inspection of a System With Unrevealed Failure and an Unrevealed Defective State

This paper proposes a model of inspection of a protection system in which the inspection outcome provides imperfect information of the state of the system. The system itself is required to operate on demand typically in emergency situations. The purpose of inspection is to determine the functional state of the system and consequently whether the system requires replacement. The system state is modeled using the delay time concept in which the failed state is preceded by a defective state. Imperfect inspection is quantified by a set of probabilities that relate the system state to the outcome of the inspection. The paper studies the effect of these probabilities on the efficacy of inspection. The analysis indicates that preventive replacement mitigates low-quality inspection and that inspection is cost-effective provided the imperfect inspection probabilities are not too large. Some derivative policies in which replacement is “postponed” following a positive inspection are also studied. An isolation valve in a utility network motivates the modeling.

The clip and the tip: Lessons learned from ablation of atrial fibrillation in patients postpercutaneous mitral valve repair.

Atrial fibrillation (AF) and higher grade mitral valve regurgitation are often associated. For both, there are interventional therapeutic options such as pulmonary vein isolation (PVI) and percutaneous mitral valve repair (PMVR) using MitraClip. This study investigated the feasibility, safety and clinical outcome of AF ablation in patients with prior PMVR. This study included patients with symptomatic AF who underwent PVI after prior PMVR at a tertiary care center (14 consecutive patients, group I). A propensity-score matched group of 42 patients (1:3 matching, group II) without prior valve repair acted as controls. Acute PVI was achieved in all patients. No difference was found regarding median procedure time (group I: 125.0 [Q1: 120.0; Q3: 176.3] vs group II: 135.0 [120.0; 177.5] minutes; P = 0.87) and median fluoroscopy duration (group I: 17.2 [12.9; 25.9] vs group II: 18.6 [12.3; 25.9] minutes; P = 0.95). In group I, one patient suffered a postprocedural transient ischemic attack. No further major complications occurred (P = 0.25). No periprocedural interference with the MitraClip was noted. The Kaplan-Meier estimate 18-month overall arrhythmia-free survival after the index procedure including a 3-month blanking period was 64.8% (95% confidence interval [CI] 42.1-99.8%) for the study group and 68.3% (95% CI, 54.6-85.6%) for the control group P = 0.35). A higher percentage of left atrial tachycardias was observed in the study group (67% vs 12% of patients with any arrhythmia recurrence; P = 0.01). Catheter ablation of AF in patients with prior PMVR is feasible and safe and results in satisfying clinical outcome.

Resonator to Laser Cavity Decoupling Interface for Chemical Oxygen Iodine Laser

In the present work, the conventional chemical oxygen iodine laser (COIL) source has been technologically upgraded and successfully tested after implementation of decoupling interface between laser cavity and resonator. In the technique, anti-reflection coated fused silica windows mounted in suitable mechanical assemblies are placed between resonator mirrors and laser cavity in such a way that the generated laser beam is out coupled through the resonator during the laser operation. The implemented decoupling assemblies isolate the caustic environment produced in low pressure laser cavity from that of resonator mirrors. Thus requirement of using isolation valves and cavity limbs between laser cavity and resonator as in conventional COIL source is eliminated. Such decoupling mechanism therefore effectively reduces the number of associated components as well as overall length of the laser source which in turn further reduces the overall weight of the laser making it suitable for use onto a mobile platform. Moreover the technique provides accrued benefits in terms of reduction in readiness time and checking of optical alignment of the laser source at will in practical operation scenarios.

Freeze-Dryer Equipment Capability Limit: Comparison of Computational Modeling With Experiments at Laboratory Scale

The equipment capability curve is one of the bounding elements of the freeze-drying design space, and understanding it is critical to process design, transfer, and scale-up. The second bounding element of the design space is the product temperature limit beyond which the product collapses. The high cost associated with freeze-drying any product renders it crucial to operate using the most efficient cycle within the limits of the equipment and the product. In this work, we present a computational model to generate the equipment capability curve for 2 laboratory scale freeze-dryers and compare the results to experimentally generated equipment capability curves. The average deviations of the modeling results from the experiments for the 2 lyophilizers modeled are −4.8% and −7.2%. In addition, we investigate the effect of various numerical and geometric parameters on the simulated equipment capability. Among the numerical parameters, the chamber wall thermal boundary conditions exert the largest influence with a maximum value of 12.3%. Among the geometric parameters, the inclusion of the isolation valve reduces the equipment capability by 23.7%. Larger isolation valves, required for controlled nucleation technology, choke the flow in the duct at lower sublimation rates, thereby lowering the equipment capability limit.

Water distribution network failure analysis under uncertainty

Failure analysis of water distribution network gains prime importance as it plays a crucial role in meeting the increasing demand for water in megacities. Water interruption can occur due to instances of component failure such as in pipes and valves. Water distribution network is a complex system comprising a variety of components and their interrelations. To avoid sub-optimization, a comprehensive framework for failure analysis is needed, in order to include all parts of water distribution network. The primary aim of the study was to propose a framework for failure analysis in which fuzzy set theory was combined with fault tree analysis as a useful model to deal with uncertainties resulting from unavailability of data. The proposed framework was applied to a water distribution network in Tehran to demonstrate its validity. Water supply interruption was considered a top event in the fault tree. As a result, the occurrence probability of top event was 0.29. According to sensitivity results, isolation valve failure was the critical minimal cut set with the value of 0.16, which shows a 55% decrease in top event probability. Thus, it is concluded that in decision-making process, a focus should be maintained on the critical minimal cut set, while suggesting corrective actions.

Use of Risk-Informed Technique to Evaluate the Balance of Technical Specifications Events

Risk-informed Technique, combining Deterministic analysis with Probabilistic Risk analysis, could evaluate the whole risk of Nuclear Power Plant, which is more and more deeply used in different areas in NPP, such as Technical Specifications, In-service inspection, GQA and so on. In Risk-informed Technical Specifications Optimization, a three-tiered approach for licensees to evaluate risk associated with proposed TS changes: Probabilistic Risk Assessment Capability and insights, Avoidance of Risk-Significant Plant Configuration, and Risk-Informed Configuration risk management. The Avoidance of Risk-Significant Plant Configuration is one of the essential links, which is also the chief content of Risk-informed Technical Specifications Optimization, so identifying the risk-signification configurations is particularly important for evaluating risk impact. This paper takes one proposed Spray isolation valve TS item change of Containment Spray System in some NPP as an example, to illustrate the method and process of Identifying Risk-significant Configuration from importance analysis result, and gives management suggestions based on the Risk-significant Configuration result, which gives a special way to analysis avoidance of risk-significant configuration, and a well practical lesson for Risk-informed application..

Thermal acoustic phenomena in a cryogenic helium distribution system

During normal operation of the cryogenic helium distribution system for the TPS superconducting radio frequency (SRF) cavities, thermal acoustic oscillations (TAO) occur leading to pressure fluctuations in the cold helium gas processing lines up to 65 mbar at a high frequency. The thermal acoustic phenomena present an additional heat load and affecting the operational stability of the SRF cavities. Three gas buffers were attached to the exhaust pipelines of the helium gas processing lines and the isolation valve of the gas buffers was kept half open to prevent pulsation in the flow. These buffers successfully suppressed the TAO phenomena without modifying the exhaust pipelines. The pressure fluctuations were reduced to not more than 7 mbar satisfying the operational requirements for the SRF cavities. In this paper, we present and discuss the solution for the thermal acoustic phenomena in the cryogenic distribution system.

Multizone Casedhole Frac Packs and Intelligent-Well Systems Improve Recovery in Subsea Gas Fields

Summary A nine–well subsea development project has been completed using casedhole frac packs (CHFPs) for sand control and multizone intelligent–well systems (IWSs) to improve recovery from a series of shallow, low–pressure gas reservoirs. In these wells, CHFPs have been installed to provide reliable sand control over the long, low–net–to–gross–ratio sand/shale target sequence: typically, three to six frac packs per well. This outer CHFP completion is then augmented with a multizone IWS, consisting of isolation seals, surface–controlled zonal–isolation valves, and downhole–pressure/temperature (DHP/T) gauges. The IWS string is run as a separate inner string to provide flow–monitoring capability and allow shutoff of zones producing high water volumes. This critical water–shutoff capability eliminates the risk of one or more high–water–production zones loading up and killing adjacent low–pressure gas zones, with the associated loss of reserves. To date, a total of nine wells have been completed and are being produced from three subsea gas fields. To maximize recovery from the fields’ numerous but relatively thin gas reservoirs, production wells are completed over three to six separate intervals. These frac–packed intervals are then grouped to allow flow control and pressure/temperature monitoring to occur through up to six surface–operated interval control valves (ICVs) and associated downhole gauges. This combination of sand control and intelligent–well control has provided an ability to perform multirate tests (MRTs) and pressure–buildup (PBU) tests on each reservoir interval to detect the start of water production or identify other impending production issues. After approximately 6 years of production service to the October 2018 date of this paper, 16 of the 34 zones completed in the nine–well project have been shut in to eliminate high water production. These water–shutoff actions performed using the surface–controlled ICVs are estimated to have improved gas–recovery factors from 50 to 60% without requiring rig intervention. This paper describes the reservoir challenges addressed and the completion–design and –operating practices used in this successful program.

Оптимизация геометрической формы проточной части разделительного клапана

Оптимизация геометрической формы проточной части разделительного клапана

Optimizing the Formation of DMAs in a Water Distribution Network through Advanced Modelling

Water pressure management in a water distribution network (WDN) is a key component applied to achieve desirable water quality as well as a trouble-free operation of the network. This paper presents a hybrid, two-stage approach, to provide optimal separation of a WDN into District Metered Areas (DMAs), improving both water age and pressure. The first stage aims to divide the WDN into smaller areas via the Geometric Partitioning method, which is based on Recursive Coordinate Bisection (RCB). Subsequently, the Student’s t-mixture model (SMM) is applied to each area, providing an optimal placement of isolation valves and separating the network in DMAs. The model is evaluated on a realistic network generated through Watergems and is compared against one variation of it implemented, including the Gaussian Mixture Model (GMM) as well as the Genetic Algorithm (GA) approach, obtaining impressive performance. The implementation of both stages was deployed in a MATLAB environment through the Epanet toolkit. The proposed system is very promising, especially for large size WDNs due to the decreased running time and noteworthy reduction of pressure and water age.

BWR-4 ATWS modeling with RELAP5-S3K

Anticipated Transients without Scram (ATWS) are evaluated to demonstrate the capability of the barriers to prevent fission product release. Swiss nuclear authority guidelines allow the use of best-estimate codes and methodologies for beyond design basis events analyses, such as ATWS, to simulate more realistic plant responses. Thus, realistic initial and boundary conditions may be applied so that all systems unaffected by the event are credited and no independent single failures need to be assumed.The RELAP5-S3K coupled thermal-hydraulics/neutronics code was used for KKM (Mühleberg BWR-4 NPP) ATWS analyses. The KKM RELAP5-S3K model was demonstrated to be valid for a wide range of transients including Loss of Coolant Accident (LOCA) and ATWS. Two ATWS cases, a main steam isolation valve (MSIV) closure and a loss of offsite power (LOOP), were simulated to demonstrate the KKM plant capability. The MSIV closure is a limiting ATWS event for reactor pressure vessel (RPV) overpressure and torus pressure and temperature. After closure of the MSIV, all RPV outlet flow is directed to the torus through the safety relief valves resulting in limiting torus pressures and temperatures comparable to other events. The LOOP event can be a limiting ATWS event for peak cladding temperature (PCT) if insufficient makeup water is available.The simulation results showed that the ATWS acceptance criteria for PCT, reactor peak pressure, and torus temperature and pressure are satisfied. The RELAP5-S3K results have been compared to the ATWS results from KKM’s fuel vendor, General Electric-Hitachi (GEH), using their TRACG code (TRACG being perhaps the most advanced system code available for BWRs). The plant response predicted by the RELAP5-S3K model is similar to that reported by GEH. Variations between the two are attributed to (1) code differences in modeling of the physical phenomena and (2) different levels of detail in modeling the KKM plant and core parameters, e.g. cross-sections.Considering that an independently developed model using the RELAP5-S3K code predicts plant behavior during an ATWS similar to the state-of-the-art code TRACG, it is concluded that the KKM ATWS analysis with RELAP5-S3K provides trustworthy information for comparison against safety criteria.